Integrated circuit and device fabrication requires deposition of electronic materials on substrates. The deposited film may be a permanent part of the substrate or finished circuit. In this case, the film characteristics are chosen to provide the electrical, physical, or chemical properties required for circuit operation. In other cases, the film may be employed as a temporary layer that enables or simplifies device or circuit fabrication. For example, a deposited film may serve as a mask for subsequent etching processes. The etch-resistant film may be patterned such that it covers areas of the substrate that are not to be removed by the etch process. A subsequent process may then remove the etch-resistant film in order to allow further processing of the substrate.
In another example of a temporary layer, a film may be employed to enhance a subsequent lithographic patterning operation. In one embodiment, a film with specific optical properties is deposited on a substrate, after which the film is coated with a photosensitive imaging film commonly referred to as photoresist. The photoresist is then patterned by exposure to light. The optical properties of the underlying deposited film are chosen to reduce reflection of the exposing light, thereby improving the resolution of the lithographic process. Such a film is commonly referred to as an anti-reflective coating (henceforth: ARC).
In another example of a temporary layer, a film may be employed that acts both as a hard mask and an antireflective coating, such as the film described in U.S. Pat. No. 6,316,167.